Cardiac-brain 'vicious circle' may increase risk for heart disease patients

10 April 2007

A region of the brain responsible for learning, memory and emotion also monitors and responds to heart performance, Wellcome Trust scientists have found. However, at times of stress, their response can actually increase the strain on the heart. The findings, published online today in 'Proceedings of the National Academy of Sciences', may provide a new insight into how cardiac arrhythmias (abnormal heart rhythms) are triggered and can lead to sudden death in patients with an underlying heart condition.

At times of stress, healthy people typically respond with increased cardiac activity, including increases in the overall output of the heart (i.e. increased heart rate and blood flow). However, these responses to stress may place patients with heart disease at risk.

Researchers at the Wellcome Trust Centre for Neuroimaging at University College London (UCL) and the Brighton and Sussex Medical School (BSMS) studied patients with specific heart conditions, measuring electrical changes at the surface of the skull to examine how the brain operates. The patients performed a mildly stressful task, counting backwards in sevens.

The scientists noted that activity in 'higher level' regions, such as the cortex, not only reflected the responses of the heart to stress, but also became involved in a 'feedback loop', often worsening the situation by destabilising the heart muscle. These regions had not previously been thought to be involved in regulating the heart's performance.

"We found a close association between the actual performance of the heart and activity in the cortex, which suggests that these brain regions listen closely to the beat-to-beat activity," says Dr Marcus Gray from BSMS. "We know that stress can increase the risk of sudden death through cardiac arrest and that the brain areas responsible for regulating heart function can be unbalanced by stress. Our research suggests that the cerebral cortex may play a significant role in these events by becoming involved in a vicious circle."

Feedback loops are a key to understanding how cardiac function is controlled, allowing it to be affected by progressively more abstract influences, beginning with information about muscle fibre stress and stretching, through to changes in blood pressure and finally to emotional or threatening stimuli.

"The basic function of cardiac feedback loops is to allow a diverse range of inputs to influence cardiac control," explains Dr Gray. "At one level there is evidence that newer brain areas (in evolutionary terms) both monitor and, conversely, can influence cardiac function. While evolutionarily older areas of the brain regulate blood pressure and blood flow, feedback loops involving newer cortical areas allow for cardiac function to be regulated to match emotional and cognitive state."

Exactly why the cortex gets involved is not clear, Dr Gray explains. However, he points to research indicating that there are fundamental links between conscious emotional experience and physiology.

Contact

Craig Brierley
Media Officer
Wellcome Trust
T +44 (0)20 7611 7329
E c.brierley@wellcome.ac.uk

Notes for editors

1. Gray MA et al. A cortical potential reflecting cardiac function. Proc Natl Acad Sci. [Epub ahead of print].

2. The Wellcome Trust is the largest charity in the UK. It funds innovative biomedical research, in the UK and internationally, spending around £500 million each year to support the brightest scientists with the best ideas. The Wellcome Trust supports public debate about biomedical research and its impact on health and wellbeing.

3. University College London
Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender, and the first to provide systematic teaching of law, architecture and medicine. In the Government's most recent Research Assessment Exercise, 59 UCL departments achieved top ratings of 5* and 5, indicating research quality of international excellence.

UCL is the fourth-ranked UK university in the 2006 league table of the top 500 world universities produced by the Shanghai Jiao Tong University. UCL alumni include Mahatma Gandhi (laws 1889, Indian political and spiritual leader); Jonathan Dimbleby (philosophy 1969, writer and television presenter); Junichiro Koizumi (economics 1969, Prime Minister of Japan); Lord Woolf (laws 1954 - Lord Chief Justice of England and Wales), Alexander Graham Bell (phonetics 1860s - inventor of the telephone), and members of the band Coldplay.

4. Brighton and Sussex Medical School is one of the most popular medical schools in the UK, with its first intake now in its fourth year. Students are taught in a research-rich environment and take part in faculty research projects. BSMS's mission is to create competent, committed and compassionate practitioners with excellent interpersonal skills and high ethical standards. For information, please contact Rehanna Neky on +44 (0)1273 877844.